/*
 * Copyright (c) 2007-2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: XPathContext.java,v 1.2.4.2 2005/09/15 01:37:55 jeffsuttor Exp $
 */
package com.sun.org.apache.xpath.internal;

import com.sun.org.apache.xalan.internal.extensions.ExpressionContext;
import com.sun.org.apache.xalan.internal.res.XSLMessages;
import com.sun.org.apache.xml.internal.dtm.Axis;
import com.sun.org.apache.xml.internal.dtm.DTM;
import com.sun.org.apache.xml.internal.dtm.DTMFilter;
import com.sun.org.apache.xml.internal.dtm.DTMIterator;
import com.sun.org.apache.xml.internal.dtm.DTMManager;
import com.sun.org.apache.xml.internal.dtm.DTMWSFilter;
import com.sun.org.apache.xml.internal.dtm.ref.sax2dtm.SAX2RTFDTM;
import com.sun.org.apache.xml.internal.utils.IntStack;
import com.sun.org.apache.xml.internal.utils.NodeVector;
import com.sun.org.apache.xml.internal.utils.ObjectStack;
import com.sun.org.apache.xml.internal.utils.PrefixResolver;
import com.sun.org.apache.xml.internal.utils.XMLString;
import com.sun.org.apache.xpath.internal.axes.SubContextList;
import com.sun.org.apache.xpath.internal.objects.DTMXRTreeFrag;
import com.sun.org.apache.xpath.internal.objects.XObject;
import com.sun.org.apache.xpath.internal.objects.XString;
import com.sun.org.apache.xpath.internal.res.XPATHErrorResources;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Stack;
import java.util.Vector;
import javax.xml.transform.ErrorListener;
import javax.xml.transform.SourceLocator;
import javax.xml.transform.TransformerException;
import javax.xml.transform.URIResolver;
import org.xml.sax.XMLReader;

/**
 * Default class for the runtime execution context for XPath.
 *
 * <p>This class extends DTMManager but does not directly implement it.</p>
 * @xsl.usage advanced
 */
public class XPathContext extends DTMManager // implements ExpressionContext
{
    IntStack m_last_pushed_rtfdtm = new IntStack();
    /**
     * Stack of cached "reusable" DTMs for Result Tree Fragments.
     * This is a kluge to handle the problem of starting an RTF before
     * the old one is complete.
     *
     * %REVIEW% I'm using a Vector rather than Stack so we can reuse
     * the DTMs if the problem occurs multiple times. I'm not sure that's
     * really a net win versus discarding the DTM and starting a new one...
     * but the retained RTF DTM will have been tail-pruned so should be small.
     */
    private Vector m_rtfdtm_stack = null;
    /** Index of currently active RTF DTM in m_rtfdtm_stack */
    private int m_which_rtfdtm = -1;

    /**
      * Most recent "reusable" DTM for Global Result Tree Fragments. No stack is
      * required since we're never going to pop these.
      */
    private SAX2RTFDTM m_global_rtfdtm = null;

    /**
     * HashMap of cached the DTMXRTreeFrag objects, which are identified by DTM IDs.
     * The object are just wrappers for DTMs which are used in  XRTreeFrag.
     */
    private HashMap m_DTMXRTreeFrags = null;

    /**
     * state of the secure processing feature.
     */
    private boolean m_isSecureProcessing = false;

    private boolean m_useServicesMechanism = true;

    /**
     * Though XPathContext context extends
     * the DTMManager, it really is a proxy for this object, which
     * is the real DTMManager.
     */
    protected DTMManager m_dtmManager = null;

    /**
     * Return the DTMManager object.  Though XPathContext context extends
     * the DTMManager, it really is a proxy for the real DTMManager.  If a
     * caller needs to make a lot of calls to the DTMManager, it is faster
     * if it gets the real one from this function.
     */
    public DTMManager getDTMManager() {
        return m_dtmManager;
    }

    /**
     * Set the state of the secure processing feature
     */
    public void setSecureProcessing(boolean flag) {
        m_isSecureProcessing = flag;
    }

    /**
     * Return the state of the secure processing feature
     */
    public boolean isSecureProcessing() {
        return m_isSecureProcessing;
    }

    /**
     * Get an instance of a DTM, loaded with the content from the
     * specified source.  If the unique flag is true, a new instance will
     * always be returned.  Otherwise it is up to the DTMManager to return a
     * new instance or an instance that it already created and may be being used
     * by someone else.
     * (I think more parameters will need to be added for error handling, and entity
     * resolution).
     *
     * @param source the specification of the source object, which may be null,
     *               in which case it is assumed that node construction will take
     *               by some other means.
     * @param unique true if the returned DTM must be unique, probably because it
     * is going to be mutated.
     * @param wsfilter Enables filtering of whitespace nodes, and may be null.
     * @param incremental true if the construction should try and be incremental.
     * @param doIndexing true if the caller considers it worth it to use
     *                   indexing schemes.
     *
     * @return a non-null DTM reference.
     */
    public DTM getDTM(javax.xml.transform.Source source, boolean unique, DTMWSFilter wsfilter, boolean incremental, boolean doIndexing) {
        return m_dtmManager.getDTM(source, unique, wsfilter, incremental, doIndexing);
    }

    /**
     * Get an instance of a DTM that "owns" a node handle.
     *
     * @param nodeHandle the nodeHandle.
     *
     * @return a non-null DTM reference.
     */
    public DTM getDTM(int nodeHandle) {
        return m_dtmManager.getDTM(nodeHandle);
    }

    /**
     * Given a W3C DOM node, try and return a DTM handle.
     * Note: calling this may be non-optimal.
     *
     * @param node Non-null reference to a DOM node.
     *
     * @return a valid DTM handle.
     */
    public int getDTMHandleFromNode(org.w3c.dom.Node node) {
        return m_dtmManager.getDTMHandleFromNode(node);
    }

    //
    //
    /**
     * %TBD% Doc
     */
    public int getDTMIdentity(DTM dtm) {
        return m_dtmManager.getDTMIdentity(dtm);
    }

    //
    /**
     * Creates an empty <code>DocumentFragment</code> object.
     * @return A new <code>DocumentFragment handle</code>.
     */
    public DTM createDocumentFragment() {
        return m_dtmManager.createDocumentFragment();
    }

    //
    /**
     * Release a DTM either to a lru pool, or completely remove reference.
     * DTMs without system IDs are always hard deleted.
     * State: experimental.
     *
     * @param dtm The DTM to be released.
     * @param shouldHardDelete True if the DTM should be removed no matter what.
     * @return true if the DTM was removed, false if it was put back in a lru pool.
     */
    public boolean release(DTM dtm, boolean shouldHardDelete) {
        // %REVIEW% If it's a DTM which may contain multiple Result Tree
        // Fragments, we can't discard it unless we know not only that it
        // is empty, but that the XPathContext itself is going away. So do
        // _not_ accept the request. (May want to do it as part of
        // reset(), though.)
        if (m_rtfdtm_stack != null && m_rtfdtm_stack.contains(dtm)) {
            return false;
        }

        return m_dtmManager.release(dtm, shouldHardDelete);
    }

    /**
     * Create a new <code>DTMIterator</code> based on an XPath
     * <a href="http://www.w3.org/TR/xpath#NT-LocationPath>LocationPath</a> or
     * a <a href="http://www.w3.org/TR/xpath#NT-UnionExpr">UnionExpr</a>.
     *
     * @param xpathCompiler ??? Somehow we need to pass in a subpart of the
     * expression.  I hate to do this with strings, since the larger expression
     * has already been parsed.
     *
     * @param pos The position in the expression.
     * @return The newly created <code>DTMIterator</code>.
     */
    public DTMIterator createDTMIterator(Object xpathCompiler, int pos) {
        return m_dtmManager.createDTMIterator(xpathCompiler, pos);
    }

    //
    /**
     * Create a new <code>DTMIterator</code> based on an XPath
     * <a href="http://www.w3.org/TR/xpath#NT-LocationPath>LocationPath</a> or
     * a <a href="http://www.w3.org/TR/xpath#NT-UnionExpr">UnionExpr</a>.
     *
     * @param xpathString Must be a valid string expressing a
     * <a href="http://www.w3.org/TR/xpath#NT-LocationPath>LocationPath</a> or
     * a <a href="http://www.w3.org/TR/xpath#NT-UnionExpr">UnionExpr</a>.
     *
     * @param presolver An object that can resolve prefixes to namespace URLs.
     *
     * @return The newly created <code>DTMIterator</code>.
     */
    public DTMIterator createDTMIterator(String xpathString, PrefixResolver presolver) {
        return m_dtmManager.createDTMIterator(xpathString, presolver);
    }

    //
    /**
     * Create a new <code>DTMIterator</code> based only on a whatToShow and
     * a DTMFilter.  The traversal semantics are defined as the descendant
     * access.
     *
     * @param whatToShow This flag specifies which node types may appear in
     *   the logical view of the tree presented by the iterator. See the
     *   description of <code>NodeFilter</code> for the set of possible
     *   <code>SHOW_</code> values.These flags can be combined using
     *   <code>OR</code>.
     * @param filter The <code>NodeFilter</code> to be used with this
     *   <code>TreeWalker</code>, or <code>null</code> to indicate no filter.
     * @param entityReferenceExpansion The value of this flag determines
     *   whether entity reference nodes are expanded.
     *
     * @return The newly created <code>NodeIterator</code>.
     */
    public DTMIterator createDTMIterator(int whatToShow, DTMFilter filter, boolean entityReferenceExpansion) {
        return m_dtmManager.createDTMIterator(whatToShow, filter, entityReferenceExpansion);
    }

    /**
     * Create a new <code>DTMIterator</code> that holds exactly one node.
     *
     * @param node The node handle that the DTMIterator will iterate to.
     *
     * @return The newly created <code>DTMIterator</code>.
     */
    public DTMIterator createDTMIterator(int node) {
        // DescendantIterator iter = new DescendantIterator();
        DTMIterator iter = new com.sun.org.apache.xpath.internal.axes.OneStepIteratorForward(Axis.SELF);
        iter.setRoot(node, this);
        return iter;
        // return m_dtmManager.createDTMIterator(node);
    }

    /**
     * Create an XPathContext instance.
     */
    public XPathContext() {
        this(true);
    }

    public XPathContext(boolean useServicesMechanism) {
        init(useServicesMechanism);
    }

    /**
     **This constructor doesn't seem to be used anywhere -- huizhe wang**
     * Create an XPathContext instance.
     * @param owner Value that can be retrieved via the getOwnerObject() method.
     * @see #getOwnerObject
     */
    public XPathContext(Object owner) {
        m_owner = owner;
        try {
            m_ownerGetErrorListener = m_owner.getClass().getMethod("getErrorListener", new Class[] {});
        } catch (NoSuchMethodException nsme) {
        }
        init(true);
    }

    private void init(boolean useServicesMechanism) {
        m_prefixResolvers.push(null);
        m_currentNodes.push(DTM.NULL);
        m_currentExpressionNodes.push(DTM.NULL);
        m_saxLocations.push(null);
        m_useServicesMechanism = useServicesMechanism;
        m_dtmManager = DTMManager.newInstance(com.sun.org.apache.xpath.internal.objects.XMLStringFactoryImpl.getFactory());
    }

    /**
     * Reset for new run.
     */
    public void reset() {
        releaseDTMXRTreeFrags();
        // These couldn't be disposed of earlier (see comments in release()); zap them now.
        if (m_rtfdtm_stack != null)
            for (java.util.Enumeration e = m_rtfdtm_stack.elements(); e.hasMoreElements();)
                m_dtmManager.release((DTM) e.nextElement(), true);

        m_rtfdtm_stack = null; // drop our references too
        m_which_rtfdtm = -1;

        if (m_global_rtfdtm != null)
            m_dtmManager.release(m_global_rtfdtm, true);
        m_global_rtfdtm = null;

        m_dtmManager = DTMManager.newInstance(com.sun.org.apache.xpath.internal.objects.XMLStringFactoryImpl.getFactory());

        m_saxLocations.removeAllElements();
        m_axesIteratorStack.removeAllElements();
        m_contextNodeLists.removeAllElements();
        m_currentExpressionNodes.removeAllElements();
        m_currentNodes.removeAllElements();
        m_iteratorRoots.RemoveAllNoClear();
        m_predicatePos.removeAllElements();
        m_predicateRoots.RemoveAllNoClear();
        m_prefixResolvers.removeAllElements();

        m_prefixResolvers.push(null);
        m_currentNodes.push(DTM.NULL);
        m_currentExpressionNodes.push(DTM.NULL);
        m_saxLocations.push(null);
    }

    /** The current stylesheet locator. */
    ObjectStack m_saxLocations = new ObjectStack(RECURSIONLIMIT);

    /**
     * Set the current locater in the stylesheet.
     *
     * @param location The location within the stylesheet.
     */
    public void setSAXLocator(SourceLocator location) {
        m_saxLocations.setTop(location);
    }

    /**
     * Set the current locater in the stylesheet.
     *
     * @param location The location within the stylesheet.
     */
    public void pushSAXLocator(SourceLocator location) {
        m_saxLocations.push(location);
    }

    /**
     * Push a slot on the locations stack so that setSAXLocator can be
     * repeatedly called.
     *
     */
    public void pushSAXLocatorNull() {
        m_saxLocations.push(null);
    }

    /**
     * Pop the current locater.
     */
    public void popSAXLocator() {
        m_saxLocations.pop();
    }

    /**
     * Get the current locater in the stylesheet.
     *
     * @return The location within the stylesheet, or null if not known.
     */
    public SourceLocator getSAXLocator() {
        return (SourceLocator) m_saxLocations.peek();
    }

    /** The owner context of this XPathContext.  In the case of XSLT, this will be a
     *  Transformer object.
     */
    private Object m_owner;

    /** The owner context of this XPathContext.  In the case of XSLT, this will be a
     *  Transformer object.
     */
    private Method m_ownerGetErrorListener;

    /**
     * Get the "owner" context of this context, which should be,
     * in the case of XSLT, the Transformer object.  This is needed
     * so that XSLT functions can get the Transformer.
     * @return The owner object passed into the constructor, or null.
     */
    public Object getOwnerObject() {
        return m_owner;
    }

    // ================ VarStack ===================

    /**
     * The stack of Variable stacks.  A VariableStack will be
     * pushed onto this stack for each template invocation.
     */
    private VariableStack m_variableStacks = new VariableStack();

    /**
     * Get the variable stack, which is in charge of variables and
     * parameters.
     *
     * @return the variable stack, which should not be null.
     */
    public final VariableStack getVarStack() {
        return m_variableStacks;
    }

    /**
     * Get the variable stack, which is in charge of variables and
     * parameters.
     *
     * @param varStack non-null reference to the variable stack.
     */
    public final void setVarStack(VariableStack varStack) {
        m_variableStacks = varStack;
    }

    // ================ SourceTreeManager ===================

    /** The source tree manager, which associates Source objects to source
     *  tree nodes. */
    private SourceTreeManager m_sourceTreeManager = new SourceTreeManager();

    /**
     * Get the SourceTreeManager associated with this execution context.
     *
     * @return the SourceTreeManager associated with this execution context.
     */
    public final SourceTreeManager getSourceTreeManager() {
        return m_sourceTreeManager;
    }

    /**
     * Set the SourceTreeManager associated with this execution context.
     *
     * @param mgr the SourceTreeManager to be associated with this
     *        execution context.
     */
    public void setSourceTreeManager(SourceTreeManager mgr) {
        m_sourceTreeManager = mgr;
    }

    // =================================================

    /** The ErrorListener where errors and warnings are to be reported.   */
    private ErrorListener m_errorListener;

    /** A default ErrorListener in case our m_errorListener was not specified and our
     *  owner either does not have an ErrorListener or has a null one.
     */
    private ErrorListener m_defaultErrorListener;

    /**
     * Get the ErrorListener where errors and warnings are to be reported.
     *
     * @return A non-null ErrorListener reference.
     */
    public final ErrorListener getErrorListener() {

        if (null != m_errorListener)
            return m_errorListener;

        ErrorListener retval = null;

        try {
            if (null != m_ownerGetErrorListener)
                retval = (ErrorListener) m_ownerGetErrorListener.invoke(m_owner, new Object[] {});
        } catch (Exception e) {
        }

        if (null == retval) {
            if (null == m_defaultErrorListener)
                m_defaultErrorListener = new com.sun.org.apache.xml.internal.utils.DefaultErrorHandler();
            retval = m_defaultErrorListener;
        }

        return retval;
    }

    /**
     * Set the ErrorListener where errors and warnings are to be reported.
     *
     * @param listener A non-null ErrorListener reference.
     */
    public void setErrorListener(ErrorListener listener) throws IllegalArgumentException {
        if (listener == null)
            throw new IllegalArgumentException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NULL_ERROR_HANDLER, null)); //"Null error handler");
        m_errorListener = listener;
    }

    // =================================================

    /** The TrAX URI Resolver for resolving URIs from the document(...)
     *  function to source tree nodes.  */
    private URIResolver m_uriResolver;

    /**
     * Get the URIResolver associated with this execution context.
     *
     * @return a URI resolver, which may be null.
     */
    public final URIResolver getURIResolver() {
        return m_uriResolver;
    }

    /**
     * Set the URIResolver associated with this execution context.
     *
     * @param resolver the URIResolver to be associated with this
     *        execution context, may be null to clear an already set resolver.
     */
    public void setURIResolver(URIResolver resolver) {
        m_uriResolver = resolver;
    }

    // =================================================

    /** The reader of the primary source tree.    */
    public XMLReader m_primaryReader;

    /**
     * Get primary XMLReader associated with this execution context.
     *
     * @return The reader of the primary source tree.
     */
    public final XMLReader getPrimaryReader() {
        return m_primaryReader;
    }

    /**
     * Set primary XMLReader associated with this execution context.
     *
     * @param reader The reader of the primary source tree.
     */
    public void setPrimaryReader(XMLReader reader) {
        m_primaryReader = reader;
    }

    // =================================================

    /** Misnamed string manager for XPath messages.  */
    // private static XSLMessages m_XSLMessages = new XSLMessages();

    //==========================================================
    // SECTION: Execution context state tracking
    //==========================================================

    /**
     * The current context node list.
     */
    private Stack m_contextNodeLists = new Stack();

    public Stack getContextNodeListsStack() {
        return m_contextNodeLists;
    }

    public void setContextNodeListsStack(Stack s) {
        m_contextNodeLists = s;
    }

    /**
     * Get the current context node list.
     *
     * @return  the <a href="http://www.w3.org/TR/xslt#dt-current-node-list">current node list</a>,
     * also referred to here as a <term>context node list</term>.
     */
    public final DTMIterator getContextNodeList() {

        if (m_contextNodeLists.size() > 0)
            return (DTMIterator) m_contextNodeLists.peek();
        else
            return null;
    }

    /**
     * Set the current context node list.
     *
     * @param nl the <a href="http://www.w3.org/TR/xslt#dt-current-node-list">current node list</a>,
     * also referred to here as a <term>context node list</term>.
     * @xsl.usage internal
     */
    public final void pushContextNodeList(DTMIterator nl) {
        m_contextNodeLists.push(nl);
    }

    /**
     * Pop the current context node list.
     * @xsl.usage internal
     */
    public final void popContextNodeList() {
        if (m_contextNodeLists.isEmpty())
            System.err.println("Warning: popContextNodeList when stack is empty!");
        else
            m_contextNodeLists.pop();
    }

    /**
     * The amount to use for stacks that record information during the
     * recursive execution.
     */
    public static final int RECURSIONLIMIT = (1024 * 4);

    /** The stack of <a href="http://www.w3.org/TR/xslt#dt-current-node">current node</a> objects.
     *  Not to be confused with the current node list.  %REVIEW% Note that there
     *  are no bounds check and resize for this stack, so if it is blown, it's all
     *  over.  */
    private IntStack m_currentNodes = new IntStack(RECURSIONLIMIT);

    //  private NodeVector m_currentNodes = new NodeVector();

    public IntStack getCurrentNodeStack() {
        return m_currentNodes;
    }

    public void setCurrentNodeStack(IntStack nv) {
        m_currentNodes = nv;
    }

    /**
     * Get the current context node.
     *
     * @return the <a href="http://www.w3.org/TR/xslt#dt-current-node">current node</a>.
     */
    public final int getCurrentNode() {
        return m_currentNodes.peek();
    }

    /**
     * Set the current context node and expression node.
     *
     * @param cn the <a href="http://www.w3.org/TR/xslt#dt-current-node">current node</a>.
     * @param en the sub-expression context node.
     */
    public final void pushCurrentNodeAndExpression(int cn, int en) {
        m_currentNodes.push(cn);
        m_currentExpressionNodes.push(cn);
    }

    /**
     * Set the current context node.
     */
    public final void popCurrentNodeAndExpression() {
        m_currentNodes.quickPop(1);
        m_currentExpressionNodes.quickPop(1);
    }

    /**
     * Push the current context node, expression node, and prefix resolver.
     *
     * @param cn the <a href="http://www.w3.org/TR/xslt#dt-current-node">current node</a>.
     * @param en the sub-expression context node.
     * @param nc the namespace context (prefix resolver.
     */
    public final void pushExpressionState(int cn, int en, PrefixResolver nc) {
        m_currentNodes.push(cn);
        m_currentExpressionNodes.push(cn);
        m_prefixResolvers.push(nc);
    }

    /**
     * Pop the current context node, expression node, and prefix resolver.
     */
    public final void popExpressionState() {
        m_currentNodes.quickPop(1);
        m_currentExpressionNodes.quickPop(1);
        m_prefixResolvers.pop();
    }

    /**
     * Set the current context node.
     *
     * @param n the <a href="http://www.w3.org/TR/xslt#dt-current-node">current node</a>.
     */
    public final void pushCurrentNode(int n) {
        m_currentNodes.push(n);
    }

    /**
     * Pop the current context node.
     */
    public final void popCurrentNode() {
        m_currentNodes.quickPop(1);
    }

    /**
     * Set the current predicate root.
     */
    public final void pushPredicateRoot(int n) {
        m_predicateRoots.push(n);
    }

    /**
     * Pop the current predicate root.
     */
    public final void popPredicateRoot() {
        m_predicateRoots.popQuick();
    }

    /**
     * Get the current predicate root.
     */
    public final int getPredicateRoot() {
        return m_predicateRoots.peepOrNull();
    }

    /**
     * Set the current location path iterator root.
     */
    public final void pushIteratorRoot(int n) {
        m_iteratorRoots.push(n);
    }

    /**
     * Pop the current location path iterator root.
     */
    public final void popIteratorRoot() {
        m_iteratorRoots.popQuick();
    }

    /**
     * Get the current location path iterator root.
     */
    public final int getIteratorRoot() {
        return m_iteratorRoots.peepOrNull();
    }

    /** A stack of the current sub-expression nodes.  */
    private NodeVector m_iteratorRoots = new NodeVector();

    /** A stack of the current sub-expression nodes.  */
    private NodeVector m_predicateRoots = new NodeVector();

    /** A stack of the current sub-expression nodes.  */
    private IntStack m_currentExpressionNodes = new IntStack(RECURSIONLIMIT);

    public IntStack getCurrentExpressionNodeStack() {
        return m_currentExpressionNodes;
    }

    public void setCurrentExpressionNodeStack(IntStack nv) {
        m_currentExpressionNodes = nv;
    }

    private IntStack m_predicatePos = new IntStack();

    public final int getPredicatePos() {
        return m_predicatePos.peek();
    }

    public final void pushPredicatePos(int n) {
        m_predicatePos.push(n);
    }

    public final void popPredicatePos() {
        m_predicatePos.pop();
    }

    /**
     * Get the current node that is the expression's context (i.e. for current() support).
     *
     * @return The current sub-expression node.
     */
    public final int getCurrentExpressionNode() {
        return m_currentExpressionNodes.peek();
    }

    /**
     * Set the current node that is the expression's context (i.e. for current() support).
     *
     * @param n The sub-expression node to be current.
     */
    public final void pushCurrentExpressionNode(int n) {
        m_currentExpressionNodes.push(n);
    }

    /**
     * Pop the current node that is the expression's context
     * (i.e. for current() support).
     */
    public final void popCurrentExpressionNode() {
        m_currentExpressionNodes.quickPop(1);
    }

    private ObjectStack m_prefixResolvers = new ObjectStack(RECURSIONLIMIT);

    /**
     * Get the current namespace context for the xpath.
     *
     * @return the current prefix resolver for resolving prefixes to
     *         namespace URLs.
     */
    public final PrefixResolver getNamespaceContext() {
        return (PrefixResolver) m_prefixResolvers.peek();
    }

    /**
     * Get the current namespace context for the xpath.
     *
     * @param pr the prefix resolver to be used for resolving prefixes to
     *         namespace URLs.
     */
    public final void setNamespaceContext(PrefixResolver pr) {
        m_prefixResolvers.setTop(pr);
    }

    /**
     * Push a current namespace context for the xpath.
     *
     * @param pr the prefix resolver to be used for resolving prefixes to
     *         namespace URLs.
     */
    public final void pushNamespaceContext(PrefixResolver pr) {
        m_prefixResolvers.push(pr);
    }

    /**
     * Just increment the namespace contest stack, so that setNamespaceContext
     * can be used on the slot.
     */
    public final void pushNamespaceContextNull() {
        m_prefixResolvers.push(null);
    }

    /**
     * Pop the current namespace context for the xpath.
     */
    public final void popNamespaceContext() {
        m_prefixResolvers.pop();
    }

    //==========================================================
    // SECTION: Current TreeWalker contexts (for internal use)
    //==========================================================

    /**
     * Stack of AxesIterators.
     */
    private Stack m_axesIteratorStack = new Stack();

    public Stack getAxesIteratorStackStacks() {
        return m_axesIteratorStack;
    }

    public void setAxesIteratorStackStacks(Stack s) {
        m_axesIteratorStack = s;
    }

    /**
     * Push a TreeWalker on the stack.
     *
     * @param iter A sub-context AxesWalker.
     * @xsl.usage internal
     */
    public final void pushSubContextList(SubContextList iter) {
        m_axesIteratorStack.push(iter);
    }

    /**
     * Pop the last pushed axes iterator.
     * @xsl.usage internal
     */
    public final void popSubContextList() {
        m_axesIteratorStack.pop();
    }

    /**
     * Get the current axes iterator, or return null if none.
     *
     * @return the sub-context node list.
     * @xsl.usage internal
     */
    public SubContextList getSubContextList() {
        return m_axesIteratorStack.isEmpty() ? null : (SubContextList) m_axesIteratorStack.peek();
    }

    /**
     * Get the <a href="http://www.w3.org/TR/xslt#dt-current-node-list">current node list</a>
     * as defined by the XSLT spec.
     *
     * @return the <a href="http://www.w3.org/TR/xslt#dt-current-node-list">current node list</a>.
     * @xsl.usage internal
     */

    public com.sun.org.apache.xpath.internal.axes.SubContextList getCurrentNodeList() {
        return m_axesIteratorStack.isEmpty() ? null : (SubContextList) m_axesIteratorStack.elementAt(0);
    }

    //==========================================================
    // SECTION: Implementation of ExpressionContext interface
    //==========================================================

    /**
     * Get the current context node.
     * @return The current context node.
     */
    public final int getContextNode() {
        return this.getCurrentNode();
    }

    /**
     * Get the current context node list.
     * @return An iterator for the current context list, as
     * defined in XSLT.
     */
    public final DTMIterator getContextNodes() {

        try {
            DTMIterator cnl = getContextNodeList();

            if (null != cnl)
                return cnl.cloneWithReset();
            else
                return null; // for now... this might ought to be an empty iterator.
        } catch (CloneNotSupportedException cnse) {
            return null; // error reporting?
        }
    }

    XPathExpressionContext expressionContext = new XPathExpressionContext();

    /**
     * The the expression context for extensions for this context.
     *
     * @return An object that implements the ExpressionContext.
     */
    public ExpressionContext getExpressionContext() {
        return expressionContext;
    }

    public class XPathExpressionContext implements ExpressionContext {
        /**
         * Return the XPathContext associated with this XPathExpressionContext.
         * Extensions should use this judiciously and only when special processing
         * requirements cannot be met another way.  Consider requesting an enhancement
         * to the ExpressionContext interface to avoid having to call this method.
         * @return the XPathContext associated with this XPathExpressionContext.
         */
        public XPathContext getXPathContext() {
            return XPathContext.this;
        }

        /**
         * Return the DTMManager object.  Though XPathContext context extends
         * the DTMManager, it really is a proxy for the real DTMManager.  If a
         * caller needs to make a lot of calls to the DTMManager, it is faster
         * if it gets the real one from this function.
         */
        public DTMManager getDTMManager() {
            return m_dtmManager;
        }

        /**
         * Get the current context node.
         * @return The current context node.
         */
        public org.w3c.dom.Node getContextNode() {
            int context = getCurrentNode();

            return getDTM(context).getNode(context);
        }

        /**
         * Get the current context node list.
         * @return An iterator for the current context list, as
         * defined in XSLT.
         */
        public org.w3c.dom.traversal.NodeIterator getContextNodes() {
            return new com.sun.org.apache.xml.internal.dtm.ref.DTMNodeIterator(getContextNodeList());
        }

        /**
         * Get the error listener.
         * @return The registered error listener.
         */
        public ErrorListener getErrorListener() {
            return XPathContext.this.getErrorListener();
        }

        /**
         * Return the state of the services mechanism feature.
         */
        public boolean useServicesMechnism() {
            return m_useServicesMechanism;
        }

        /**
         * Set the state of the services mechanism feature.
         */
        public void setServicesMechnism(boolean flag) {
            m_useServicesMechanism = flag;
        }

        /**
         * Get the value of a node as a number.
         * @param n Node to be converted to a number.  May be null.
         * @return value of n as a number.
         */
        public double toNumber(org.w3c.dom.Node n) {
            // %REVIEW% You can't get much uglier than this...
            int nodeHandle = getDTMHandleFromNode(n);
            DTM dtm = getDTM(nodeHandle);
            XString xobj = (XString) dtm.getStringValue(nodeHandle);
            return xobj.num();
        }

        /**
         * Get the value of a node as a string.
         * @param n Node to be converted to a string.  May be null.
         * @return value of n as a string, or an empty string if n is null.
         */
        public String toString(org.w3c.dom.Node n) {
            // %REVIEW% You can't get much uglier than this...
            int nodeHandle = getDTMHandleFromNode(n);
            DTM dtm = getDTM(nodeHandle);
            XMLString strVal = dtm.getStringValue(nodeHandle);
            return strVal.toString();
        }

        /**
         * Get a variable based on it's qualified name.
         * @param qname The qualified name of the variable.
         * @return The evaluated value of the variable.
         * @throws javax.xml.transform.TransformerException
         */

        public final XObject getVariableOrParam(com.sun.org.apache.xml.internal.utils.QName qname) throws javax.xml.transform.TransformerException {
            return m_variableStacks.getVariableOrParam(XPathContext.this, qname);
        }

    }

    /**
      * Get a DTM to be used as a container for a global Result Tree
      * Fragment. This will always be an instance of (derived from? equivalent to?)
      * SAX2DTM, since each RTF is constructed by temporarily redirecting our SAX
      * output to it. It may be a single DTM containing for multiple fragments,
      * if the implementation supports that.
      *
      * Note: The distinction between this method and getRTFDTM() is that the latter
      * allocates space from the dynamic variable stack (m_rtfdtm_stack), which may
      * be pruned away again as the templates which defined those variables are exited.
      * Global variables may be bound late (see XUnresolvedVariable), and never want to
      * be discarded, hence we need to allocate them separately and don't actually need
      * a stack to track them.
      *
      * @return a non-null DTM reference.
      */
    public DTM getGlobalRTFDTM() {
        // We probably should _NOT_ be applying whitespace filtering at this stage!
        //
        // Some magic has been applied in DTMManagerDefault to recognize this set of options
        // and generate an instance of DTM which can contain multiple documents
        // (SAX2RTFDTM). Perhaps not the optimal way of achieving that result, but
        // I didn't want to change the manager API at this time, or expose
        // too many dependencies on its internals. (Ideally, I'd like to move
        // isTreeIncomplete all the way up to DTM, so we wouldn't need to explicitly
        // specify the subclass here.)

        // If it doesn't exist, or if the one already existing is in the middle of
        // being constructed, we need to obtain a new DTM to write into. I'm not sure
        // the latter will ever arise, but I'd rather be just a bit paranoid..
        if (m_global_rtfdtm == null || m_global_rtfdtm.isTreeIncomplete()) {
            m_global_rtfdtm = (SAX2RTFDTM) m_dtmManager.getDTM(null, true, null, false, false);
        }
        return m_global_rtfdtm;
    }

    /**
     * Get a DTM to be used as a container for a dynamic Result Tree
     * Fragment. This will always be an instance of (derived from? equivalent to?)
     * SAX2DTM, since each RTF is constructed by temporarily redirecting our SAX
     * output to it. It may be a single DTM containing for multiple fragments,
     * if the implementation supports that.
     *
     * @return a non-null DTM reference.
     */
    public DTM getRTFDTM() {
        SAX2RTFDTM rtfdtm;

        // We probably should _NOT_ be applying whitespace filtering at this stage!
        //
        // Some magic has been applied in DTMManagerDefault to recognize this set of options
        // and generate an instance of DTM which can contain multiple documents
        // (SAX2RTFDTM). Perhaps not the optimal way of achieving that result, but
        // I didn't want to change the manager API at this time, or expose
        // too many dependencies on its internals. (Ideally, I'd like to move
        // isTreeIncomplete all the way up to DTM, so we wouldn't need to explicitly
        // specify the subclass here.)

        if (m_rtfdtm_stack == null) {
            m_rtfdtm_stack = new Vector();
            rtfdtm = (SAX2RTFDTM) m_dtmManager.getDTM(null, true, null, false, false);
            m_rtfdtm_stack.addElement(rtfdtm);
            ++m_which_rtfdtm;
        } else if (m_which_rtfdtm < 0) {
            rtfdtm = (SAX2RTFDTM) m_rtfdtm_stack.elementAt(++m_which_rtfdtm);
        } else {
            rtfdtm = (SAX2RTFDTM) m_rtfdtm_stack.elementAt(m_which_rtfdtm);

            // It might already be under construction -- the classic example would be
            // an xsl:variable which uses xsl:call-template as part of its value. To
            // handle this recursion, we have to start a new RTF DTM, pushing the old
            // one onto a stack so we can return to it. This is not as uncommon a case
            // as we might wish, unfortunately, as some folks insist on coding XSLT
            // as if it were a procedural language...
            if (rtfdtm.isTreeIncomplete()) {
                if (++m_which_rtfdtm < m_rtfdtm_stack.size())
                    rtfdtm = (SAX2RTFDTM) m_rtfdtm_stack.elementAt(m_which_rtfdtm);
                else {
                    rtfdtm = (SAX2RTFDTM) m_dtmManager.getDTM(null, true, null, false, false);
                    m_rtfdtm_stack.addElement(rtfdtm);
                }
            }
        }

        return rtfdtm;
    }

    /** Push the RTFDTM's context mark, to allows discarding RTFs added after this
     * point. (If it doesn't exist we don't push, since we might still be able to
     * get away with not creating it. That requires that excessive pops be harmless.)
     * */
    public void pushRTFContext() {
        m_last_pushed_rtfdtm.push(m_which_rtfdtm);
        if (null != m_rtfdtm_stack)
            ((SAX2RTFDTM) (getRTFDTM())).pushRewindMark();
    }

    /** Pop the RTFDTM's context mark. This discards any RTFs added after the last
     * mark was set.
     *
     * If there is no RTF DTM, there's nothing to pop so this
     * becomes a no-op. If pushes were issued before this was called, we count on
     * the fact that popRewindMark is defined such that overpopping just resets
     * to empty.
     *
     * Complicating factor: We need to handle the case of popping back to a previous
     * RTF DTM, if one of the weird produce-an-RTF-to-build-an-RTF cases arose.
     * Basically: If pop says this DTM is now empty, then return to the previous
     * if one exists, in whatever state we left it in. UGLY, but hopefully the
     * situation which forces us to consider this will arise exceedingly rarely.
     * */
    public void popRTFContext() {
        int previous = m_last_pushed_rtfdtm.pop();
        if (null == m_rtfdtm_stack)
            return;

        if (m_which_rtfdtm == previous) {
            if (previous >= 0) // guard against none-active
            {
                boolean isEmpty = ((SAX2RTFDTM) (m_rtfdtm_stack.elementAt(previous))).popRewindMark();
            }
        } else
            while (m_which_rtfdtm != previous) {
                // Empty each DTM before popping, so it's ready for reuse
                // _DON'T_ pop the previous, since it's still open (which is why we
                // stacked up more of these) and did not receive a mark.
                boolean isEmpty = ((SAX2RTFDTM) (m_rtfdtm_stack.elementAt(m_which_rtfdtm))).popRewindMark();
                --m_which_rtfdtm;
            }
    }

    /**
     * Gets DTMXRTreeFrag object if one has already been created.
     * Creates new DTMXRTreeFrag object and adds to m_DTMXRTreeFrags  HashMap,
     * otherwise.
     * @param dtmIdentity
     * @return DTMXRTreeFrag
     */
    public DTMXRTreeFrag getDTMXRTreeFrag(int dtmIdentity) {
        if (m_DTMXRTreeFrags == null) {
            m_DTMXRTreeFrags = new HashMap();
        }

        if (m_DTMXRTreeFrags.containsKey(new Integer(dtmIdentity))) {
            return (DTMXRTreeFrag) m_DTMXRTreeFrags.get(new Integer(dtmIdentity));
        } else {
            final DTMXRTreeFrag frag = new DTMXRTreeFrag(dtmIdentity, this);
            m_DTMXRTreeFrags.put(new Integer(dtmIdentity), frag);
            return frag;
        }
    }

    /**
     * Cleans DTMXRTreeFrag objects by removing references
     * to DTM and XPathContext objects.
     */
    private final void releaseDTMXRTreeFrags() {
        if (m_DTMXRTreeFrags == null) {
            return;
        }
        final Iterator iter = (m_DTMXRTreeFrags.values()).iterator();
        while (iter.hasNext()) {
            DTMXRTreeFrag frag = (DTMXRTreeFrag) iter.next();
            frag.destruct();
            iter.remove();
        }
        m_DTMXRTreeFrags = null;
    }
}
